The present invention relates to trailers for carrying vehicles and movable equipment with a low ground clearance, and more particularly to a trailer in which the trailer bed will simultaneously rollback and tilt into a loading position so that a cargo vehicle or movable equipment with low ground clearance may be driven, pushed, or pulled onto the trailer bed.
Apparatuses for towing or transporting vehicles have been around for a long time. One of the more recent devices for transporting automobiles is tilt-bed trucks in which the bed of the truck tilts so that the back edge of the trailer bed is adjacent to the ground. A winch is then used to pull the automobile up onto the trailer bed. After the automobile is loaded on the trailer bed, it is tilted back to a horizontal position for transporting the vehicle to another location. The problem with this current type of tilt-bed trailer is that the load angle is typically about 45xc2x0. Because of this high load angle, only vehicles with a large road clearance may be loaded for transportation. Therefore, the current form of tilt bed trucks and trailers does not allow the loading and unloading of cargo vehicles and movable equipment that has a low ground clearance Examples of movable equipment with low ground clearance includes paving equipment, which has a maximum load angle of about 7xc2x0.
Current apparatuses and methods for loading cargo vehicles and movable equipment with a low clearance include the use of ramps. Oftentimes a low flat trailer will include removable or hydraulic ramps for loading or unloading cargo vehicles or movable equipment. The ramps are either (1) carried with the trailer and are attached to the rear portion of the trailer bed for loading and unloading, or (2) are hydraulically attached to the rear portion of the trailer and are raised or lowered for loading and unloading. The cargo vehicle may then be driven, pushed or pulled onto or off of the trailer bed.
The problem with the use of ramps is that the junction between the ramp and the trailer bed forms an angled corner, and the tires of the cargo vehicle rest on a geometric plane. After the front tires move onto the trailer bed, the angled corner will protrude beyond the geometric plane to a point that approached the bottom of the cargo vehicle. If the ramp is too steep, the angled corner will protrude beyond the geometric plane and strike the bottom of the cargo vehicle. Therefore, cargo vehicles that have a very low ground clearance require extra long ramps in order to minimize the angled corner.
Different problems are caused if the cargo vehicle has continuous tracks such as the tracks of a bulldozer. The cargo vehicle will continue to move at the same angle of the ramp even as it moves beyond the ramp. The cargo vehicle will then drop down onto the trailer bed after more than 50% of its weight moves beyond the angled corner. The impact caused by the drop may cause damage to the trailer or the cargo vehicle. Again, extra long ramps must be used in order to minimize this problem.
The use of extra long hydraulic ramps is impractical. If the ramp forms a portion of the trailer bed, it cannot extend forward of the trailer wheels and suspension. As a result, extra long ramps would have to extend behind the tires a great distance resulting in design problems that would make the trailer unsafe and difficult to pull. If the hydraulic ramp was hinged to the rear end of the trailer, the ramp would extend into the air a great distance when it is moved up into a vertical position for transport. This projection into the air would cause alternative problems including a potential increase in the clearance height of the truck/trailer and a loss of gas mileage because of poor aerodynamics.
An additional problem with detachable ramps is that they may be forgotten or lost during transport. If this happens, the cargo vehicle or movable equipment may not be loaded onto or unloaded from the trailer bed.
An alternative method to solving the problem of loading cargo vehicles and movable equipment is the use of trailers that have a bed that is permanently oriented at an angle. In this situation the ramps are used to extend the length of trailer bed so that it reaches the ground. Cargo vehicles may then be loaded or unloaded. The problem with this design is the cargo vehicle secure a constant force on the straps and chains that exert it to the trailer bed and there is a much greater chance that the cargo vehicle will break loose during transport and roll off the back of the trailer. Additionally, the detachable extension ramps may be forgotten or lost.
Yet another solution to the problem is detachable goose neck trailers. These are semi-truck trailers in which the front end of the trailer is attached to a goose neck. The opposite side of the goose neck is attached to the king pin. In operation, a hydraulic system will lower the front end of the trailer bed until it reaches the ground, and the goose neck is then detached. A cargo vehicle or movable equipment may then be loaded onto the trailer bed. The goose neck is then reattached and the front end of the trailer bed is raised for transport. The difficulty with this system is that it is cumbersome to use and is only practical for a semi-truck trailer. Thus, the trailer is more expensive and requires the purchase of an expensive semi-truck.
Therefore, there remains need for a trailer that may be towed by different types of trucks and is able to provide a minimal loading angle in order to permit the loading and unloading of load vehicles and movable equipment having a very low clearance.
Furthermore, the present invention eliminates the need for any type of a loading ramp, permanently angled trailer bed, or detachable goose neck.
The present invention consists of a frame and a deck that is mounted on and supported by the frame. The invention further has a hydraulic cylinder for selectively moving the deck between a substantially horizontal load-carrying position and an inclined loading position. When the deck is in the inclined loading position, the rear portion of the deck is proximate to the ground so that a cargo vehicle or movable equipment may be driven, pushed, or pulled onto the deck. Furthermore, the angle of the deck is less than 10xc2x0.
A more specific description of a preferred embodiment of the invention is a tilt-bed trailer that has a frame and a deck mounted on and supported by the frame. The deck is movable and tiltable between a horizontal load-carrying position and an inclined loading position. The invention further has an angled track connected to the frame for guiding rollers that are attached to a front portion of the deck. A hydraulic cylinder is connected between the deck and the frame. When the hydraulic cylinder moves into a retracted configuration, the deck is caused to move rearward, and the tracks force the front end of the deck to move in an upward direction, thereby tilting the deck. When the deck is moved to its full rearward position, i.e. when the rollers of the deck are moved to the rear ends of the tracks, the rear portion of the deck is proximate to the ground so that cargo with a low ground clearance may be driven, pushed, or pulled onto the deck. The hydraulic cylinder may then be moved into an extended configuration, which causes the deck to move in a forward direction, and the track forces the front of the trailer to move downward, thereby causing the deck to move into a horizontal load carrying position. The hydraulic cylinder is anchored to the frame in such a manner that the hydraulic cylinder remains parallel to the deck at all times, regardless of whether the trailer bed is in the horizontal load-carrying position or the inclined loading position.
These and other advantages of the present invention will become apparent from the more detailed description of the preferred embodiment that follows.